1. Field of the Invention
This invention relates generally to furnaces and, more particularly, a method and apparatus for detecting incomplete combustion in a furnace.
2. Description of the Related Art
Generally, complete combustion is the reaction between a hydrocarbon and oxygen that results in the formation of water vapor and carbon dioxide to release heat. A combustion reaction in which carbon monoxide (CO) is formed from a hydrocarbon is incomplete combustion or partial combustion. Incomplete combustion occurs when there is an insufficient amount of oxygen to react with the hydrocarbon resulting in CO, a poisonous gas. CO is also formed from other factors such as quenching a combustion process. Furnace systems are designed to run the combustion reaction with an excess of oxygen so that complete combustion can take place and the maximum amount of heat may be released from the hydrocarbon fuel. Therefore, incomplete combustion is undesirable in a furnace system that uses combustion to generate heat. In addition, incomplete combustion can adversely affect the function of the furnace system, such as, for example, decreasing efficiency.
Currently, residential furnaces do not have a detection system for directly monitoring the concentration of carbon monoxide or other gasses present in combustion products due to feasibility including high cost. Pressure switches provide a mechanism to ensure proper airflow in furnaces. The pressure switches are only activated when the proper amount of airflow is reached. In an event the minimum amount of airflow is not reached the furnace shuts down. In the furnace system, the pressure switches, undesirably, only deactivate the furnace system if there is an air blockage or starvation of combustion air.
Commercially available sensors, generally, are not used in fuel-fired furnaces due to the high cost of the sensor technology. Newly developed CO sensors are smaller and less expensive so they are better suited in this regard. Oxygen, carbon dioxide and hydrocarbon gas sensors are also functional for the purposes of detecting incomplete combustion. Temperature in furnaces can cause sensor failure. Excessive temperatures, such as temperatures greater than about 550° F., can cause sensor damage and failure. Tubing or sample pumps may be used to remove sensors from harsh temperature and humidity conditions.
Accordingly, there is a need for an improvement in applying sensors that detect incomplete combustion in a furnace.